This application pertains to motion converting mechanisms, and more particularly, to mechanisms which rotate reciprocating valves on internal combustion engines.
It is common to rotate exhaust valves in internal combustion engines for reducing burning, deposit build-up and high stresses. One well known type of valve rotator is described in U.S. Pat. No. 2,624,323 issued Jan. 6, 1953, to Thorne. In the Thorne device, a pair of flanges or housing members are movable relative to each other axially and rotatably. Shiftable balls are provided between the flanges to impart rotation to one flange relative to the other during axial movement of the flanges toward each other. The rotatable flange is secured to the valve stem to rotate the valve. The valve is normally biased to a closed position by a valve spring which also acts against one of the flanges to urge it toward the other flange. When the valve is closed, the two flanges must be held axially separated from one another so that they will subsequently move toward one another upon opening of the valve. In the Thorne device, a belleville spring washer or other biasing means separate from the shiftable balls provides the biasing force necessary to hold the two parts away from each other when the valve is closed. When the valve opens, the force applied by the valve spring increases and overcomes the separating force of the belleville spring so that the two parts move toward one another and the balls to impart rotation to one of the flanges as the balls move along ramps between the flanges.
In another known valve rotator, such as shown in U.S. Pat. No. 2,758,583 issued Aug. 14, 1956, to Norton, a coil spring is positioned between two flanges. The coils of the spring are deflected when the flanges move toward one another to provide relative rotation between the flanges. In this rotator, a separate belleville spring or other separate biasing means is also used to hold the parts separated from one another when the valve is closed.
Valve rotators which do not utilize belleville spring washers or other separate biasing elements to separate the two flanges are disclosed in U.S. Pat. Nos. 2,775,232; 2,875,740; and 2,935,058. These patents are concerned with devices which will rotate a valve and/or maintain a constant force between a rocker arm and valve stem to prevent noise. In these devices, balls disposed between a pair of flanges are urged toward the shallow portions of ramps by springs. These springs are relatively weak and cannot apply a large enough force against the balls to overcome the valve spring which urges the valve closed. If the ball biasing springs were strong enough to overcome the valve spring, the flanges would separate and the valve would be forced to open slightly.